More than 50 Britons have been infected with the 'Mu' Covid variant which experts fear is resistant to vaccines, official data shows.
Public Health England said it had detected 53 cases of the mutant strain after it first cropped up in the UK in May.
No-one has died from the variant by the most recent count on August 30, but five people have been admitted to hospital with it.
PHE sources told MailOnline today they were 'not concerned' about the mutant virus, although its rapid spread in the US has led to growing concerns globally.Insurance Loans Mortgage Attorney Credit Lawyer
Mu has already been reported in every state except Nebraska, with Florida and California recording 384 cases each.
In total about 1,750 Americans have been infected with the virus according to variant tracking website outbreak.info, but it's not clear how many were hospitalised.
PHE has admitted the strain, also known as B.1.621, has some ability to evade jabs but the agency has taken confidence from the fact it is not rapidly growing.
A source told MailOnline: 'This is not really one we are hugely concerned about.'
Despite spreading into every state in the US the varaint is still at very low numbers, and accounts for 0.2 per cent of all cases in the worst-hit area California.
Studies suggest it may be better able to evade vaccines, as was the case with the South African 'Beta' variant. There are also suggestions it is more infectious than the original strain.
It was determined a 'variant of interest' by the World Health Organization last week.
The above graph shows cases of the mutant strain in the UK since June (black line - average percentage of cases down to the variant per week, and pink area - the range for the percentage). It reveals that they have remained at very low numbers, making up less than 0.1 per cent of all infections checked for variants. PHE sources told MailOnline they were not 'hugely concerned' by the variant
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The above graph shows cases of the 'Mu' variant detected globally. The average number of cases peaked (black line) in mid-July before falling
The above graph shows cases of the mutant strain in the US since April. Its prevalence peaked in May, before cases began to decline amid the spread of the Delta variant (black line, average percentage of cases sparked by the variant)
More than 4,000 cases of the variant have been detected to date and it has spread to more than 40 countries
More than 4,000 cases of B.1.621 have been spotted globally, and it has spread to more than 40 countries.
It was first detected in Colombia in January this year, where sequencing suggests it still makes up the majority of cases.
But across the world cases of the mutant strain are not surging, indicating it may be less of a threat than first feared.
Where have the cases been detected?
This mutant strain was first spotted in Colombia in January.
It has since spread to more than 40 countries including the UK, US, France, Japan and Canada.
Is it increasing in prevalence?
There have been 4,315 cases detected to date, but this is thought to be an underestimate because many countries that have suffered outbreaks do very little surveillance for variants.
The number of cases blamed on the variant declined